One type of display sign often used at convenience stores and at gasoline stations utilizes numbers located on cards that can be readily changed. The numbers identify prices, such as for cigarettes. The cards are mounted to a plate of the sign by a hinge, allowing each card to be flipped or folded from a lower position below the hinge to an upper position above the hinge. Half of the number to be displayed is on the backside of the upper card and the other half is on the front side of the lower card. A latch will latch the card located in the upper position in place.
One prior art latch comprises a rotatable retaining member that has a lobe portion that overlies an edge of the card when rotated to the retained position. The retaining member rotates about an axis that is perpendicular to the plane containing the plate.
One problem with this type of sign is that the latch does not lock in place. The retaining member may be freely rotated by anyone that can reach it. Consequently, if the sign is accessible to customers, it is possible for a customer to move the retaining member to a released position and flip the cards to change the price displayed. At times, customers demand that the product be sold at the erroneous price.